It is known to use optical fibers to transmit signals in a robot. For example, JP2015-174208A discloses a robot in which optical communication is performed through a signal line to reduce noise interference caused by capacitive coupling between the signal line and the power line. Particularly, JP2015-174208A discloses disposing an optical communication unit on a pivot shaft of a joint connecting first and second arms (links) of the robot, wherein the optical communication unit includes an optical transmitter and an optical receiver.
A robot typically includes multiple joints connecting multiple links, and it may be conceived to provide controllers on the links of the robot to control the joints. To allow the controllers to operate cooperatively to appropriately control the attitude of the robot, it is necessary to communicably connect the controllers with each other. For this purpose, each controller may be equipped with an optical transceiver unit, such that the optical transceiver units of different controllers are connected via optical fiber cables to constitute an optical fiber network to transmit optical signals for controlling the joints of the robot in a coordinated manner. Each optical fiber cable used in the communication between the optical transceiver units provided on different links may be routed to pass through multiple joints each including one or more pivot shafts. The optical fiber cable passed through the joints may be bent at each joint, and an optical signal carried on the optical fiber is attenuated at each bend of the optical fiber cable. In a case where the optical signal transmitted from one optical transceiver unit passes through many bends formed at joints, the power of the optical signal may be attenuated to such an extend that, when the optical signal is received by another optical transceiver unit after having propagated through the optical fiber cable, the power of the optical signal may be insufficient for the other optical transceiver unit to receive and process the optical signal.